1. Field of the Invention
The present invention relates to the utilization of permanent magnets made of hard magnetic powder of ferrite, alnico, rare-earth and the like materials solidified with synthetic resin and then magnetized. More particularly, it relates to an improvement is magnetic material fastener means made of permanent magnet which is provided with magnetic plates at its magnetic poles.
2. Description of the Prior Art
In the case of a magnetic fastener means, magnetic flux of a small size permanent magnet must be converged at each of the magnetic poles to obtain more intensified force of magnetism. For this purpose, a magnetic pole plate is attached to a magnetic pole. Since less expensive sintered magnets such as ferrite and alnico magnet are used for magnetic fastener means for economic reasons, they are likely to break and it was heretofore necessary to protect the peripheral surface of the magnet with a metal case.
Various improvements have been made on magnetic fastener means utilizing the magnetic force of a permanent magnet. The inventor made a magnetic fastener means substantially as shown in FIG. 30 utilizing the magnetic force of a permanent magnet 100. A magnetic pole plate 101, 102 each is attached to the N-S poles of the magnet 100 to converge the magnetic flux thereof at the pole plates 100 and 102 for effecting contact between ferromagnetic projections 101a and 102a provided on the pole plates 101 and 102, respectively. These improvements have been published as U.S. Pat. No. 4,012,891 and No. 4,453,294 issued in the name of this applicant.
The outstanding merit of Morita's improvements lies in that a hole 100a (FIG. 30) is provided directed toward the N-S poles of the magnet 100 so that the magnetic pole plate 102 of a female fastener member B' and the plate 101 of a male fastener member A' at the N-S poles respectively are made to contact at the projections 101a and 102a in said hole 100a.
As a result, the magnetic flux of the permanent magnet 100 is converged at the plates 101 and 102 at the N-S poles. At the same time a passage is constructed passing through the hole 100a which is considered magnetically neutral. The passage extending between the two poles has less magnetic reluctance. By contacting the male member A' and the female member B' of the magnetic fastener in said magnetic passage made in the hole 100a, these two members can be attracted strongly to each other.
In the magnetic fastener means according to applicants inventions in U.S. Pat. No. 4,012,891 and No. 4,453,294, it was necessary to provide a cover member 103 for protecting the magnet where magnetic pole plate 101 is attached as shown in FIG. 30 since the permanent magnet used in the fastener means was hard and brittle sintered magnetic material such as a ferrite magnet. The cover member 103 was also used to protect the magnet 100 from breaking.
Use of the cover member 103 for protecting the magnet 100 has a number of disadvantages one of which is that when the magnetic pole plate 102 is attached to the magnetic pole of the magnet 100 by the cover member 103, a small interstice X is formed between the plate 102 and the magnet 100, and the interstice X constitutes high reluctance zone to the passage of the magnetic.
The pole plate 101 of the male fastener member B' to be attracted by the female fastener member B' is in effect attracted by the magnetic pole of the magnet 100 via the cover member 103. Thus, there will be formed an additional interstice X' forming high magnetic reluctance.
However, it was not possible to omit the use of the cover member 103 in the conventional magnetic fasteners. Since the cover member 103 constituted a passage for magnetism communicating the magnetic pole plates 101 and 102 and since the cover member 103 was made of non-magnetic material for preventing the magnetic flux from leaking to outside the projections 101a and 102a (or the cover member 103), it was not possible to avoid the formation of interstice X' where magnetic reluctance occurs.